45 CFR §2400.57

1. (a)The Foundation may suspend or terminate the payment of a stipend if a Fellow fails to meet the criteria set forth in § 2400.40 through § 2400.44 and § 2400.60, except as provided for in § 2400.61. Before it suspends or terminates a fellowship under these circumstances, the Foundation will give notice to the Fellow, as well as the opportunity to be heard with respect to the grounds for suspension or termination.
2. (b)The Foundation will normally suspend the payment of a stipend if a Fellow has more than one grade of “Incomplete” in courses for which the Foundation has made payment to the Fellow.